MATLAB is a powerful programming language and environment that is widely used in scientific and engineering fields. One of the key features of MATLAB is its ability to define and use functions. Functions allow you to encapsulate a piece of code that performs a specific task, making your code more modular, reusable, and easier to understand. In this guide, we will explore how to write and use MATLAB functions effectively.
Step 1: Understanding Function Syntax
In MATLAB, functions are defined using the keyword "function" followed by the name of the function. The basic syntax for defining a function in MATLAB is as follows:
```
function [output1,output2,...] = functionName(input1,input2,...)
% Function body
% Perform computations here
% Assign output variables
end
```
The square brackets [] enclose the output variables (if any), followed by an equal sign (=) after which comes the name of the function. The input variables are listed inside parentheses (), separated by commas if there are multiple inputs.
Step 2: Writing Function Body
The function body contains all the computations that need to be performed when calling this specific function. This can include variable assignments, loops, conditional statements, mathematical operations, or even calls to other functions.
For example:
```matlab
function y = square(x)
% Compute square of input value x
y = x^2;
end
% Calling this function:
result = square(5);
disp(result); % Output: 25
```
In this example, we defined a simple `square` function that takes an input value `x` and returns its square `y`. Inside the body of our function definition (`y = x^2;`), we perform our computation by raising `x` to the power of 2 using exponentiation operator (^). Finally, we assign `y` as our output variable.
Step 3: Specifying Output Variables
If your function needs to return multiple values, you can specify them inside the square brackets [] in the function definition. For example:
```matlab
function [meanVal, varVal] = statistics(data)
% Compute mean and variance of input data
meanVal = mean(data);
varVal = var(data);
end
% Calling this function:
data = [1, 2, 3, 4, 5];
[meanValue, varianceValue] = statistics(data);
disp(meanValue); % Output: 3
disp(varianceValue); % Output: 2.5
```
In this example, we defined a `statistics` function that takes an input array `data`, calculates its mean and variance using built-in MATLAB functions (`mean` and `var`) respectively. We assigned these calculated values to our output variables `meanVal` and `varVal`.
Step 4: Saving Functions in MATLAB Files
To use functions effectively in MATLAB, it is essential to save them as separate files with a .m extension. The file name should match the name of the function.
For instance:
- Create a new text file called "square.m" containing our earlier-defined `square` function.
- Save it with .m extension (e.g., square.m).
- Place this file in a location accessible by MATLAB (e.g., current working directory or add necessary folders to MATLAB's search path).
Once saved as an .m file, you can call your custom functions from any script or command window within MATLAB using their defined names.
Step 5: Function Documentation (Optional)
It is considered good practice to provide documentation for your functions so that others (including yourself) understand how to use them correctly. You can add comments at the beginning of your function code block or create separate help files explaining its purpose and usage.
For example:
```matlab
function [meanVal, varVal] = statistics(data)
% STATISTICS Calculate mean and variance of input data.
% [MEANVAL, VARVAL] = STATISTICS(DATA) computes the mean and variance
% of the input data provided as DATA array. Returns MEANVAL as the computed
% mean value and VARVAL as the computed variance.
meanVal = mean(data);
varVal = var(data);
end
```
In this example, we added a comment block at the beginning of our `statistics` function to describe its purpose, inputs, and outputs.
By following these steps and best practices, you can write efficient MATLAB functions that enhance code organization, reusability, and readability.